Engines that actually require Thick or Thin oil?

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On BITOG it seems like viscosity is personal preference. There are guys putting 5W40 in their Prius and guys like Dr. Haas putting 0W20 in a Ferrari.

Aren't engines designed to use a specific viscosity range based on clearances? I know the operating conditions will affect viscosity, but on modern water cooled cars do you really need to adapt the oil to the operating conditions? Is this an old fashioned type of thinking that's not as relevant today? Don't modern variable valve timing systems also need a specific oil viscosity?

Are there engines that don't do so well if you use an oil too thin or too thick? Or can you just run whatever you want?
 
The owners manual has a temp compensated viscosity chart. Most people would do well to follow it. If you live in Antarctica you may need to adjust the viscosity some. Or are driving a car at the Indy 500.
 
You've been here 4 years...what have you absorbed from what you've read ?

Use your owner's manual in the market in which it is intended, for the typical usage pattern within that market, and you negate both of the bookend examples that you've stated.
 
My 65 VW Bug runs and sounds best on straight 30 wt. I have tried others but it just sounds and runs quieter on straight 30wt. My 75 Westfalia prefers 20-50.
 
Oh NO!! Another "Thick VS Thin" thread!
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Originally Posted By: tig1
Oh NO!! Another "Thick VS Thin" thread!
28.gif
18.gif
Trolling.gif



Here it is another tig1 post that he didn't get in first extolling the fact that he ran 5W20 before Ali Hass, in an engine that called for 10W40, and showing the flogging horse emoticon.
 
At one time I remember reading that older (2007) Hyundai / Kia 3.8L V-6 engines needed thinner (5W20) oil due to thinner oil passages - but I could never confirm because the OM indicated 5W20 , 5W30 or 10W30 were all fine (depending on ambient temps) .
 
Before you can run thicker oil than is listed in the owner's manual, one should be required to submit evidence in the form of plastigauge measurement of bearing clearance from all main bearings.
 
My SantaFe owners manual says I can run 5-20 or 20-50 depending on the temperature. I always use 5-30
 
You have two choices. Run what your owners manual calls for, or run the weight of your choosing.
 
When I build a Ford V8 for drag strip duty, engines with rod clearance more than .0025 get 15w-50 sun or 20w-50 conventional. Bearing clearances under .0025 get 10w-30 or 5w-30. The reason should be quite obvious. I typically like to build engines on the loose side, .0025 to .0030, especially big blocks. Connecting rod big ends do not stay round at 6,000 RPM, and the extra .0005 to .001 give an extra measure of insurance against poking through the oil film.

On a stock street car engine, everything gets xw-30. No reason to deviate from this.
 
Originally Posted By: rooflessVW
Supposedly the 5.7 Hemi "needs" a -20.

I prefer my oils to end with a -40 or -50.


I change the oil in the farm truck used for the 4-H club. It gets the cheapest 15-40 all fleet they can find, once a year. Can’t tell a lick of difference. It’s a 2007 Ram 2500 with a 5.7 Hemi. I have 7 quarts of clearance PP Euro 0-40 on my shelf, I may use it next time. Again, doubt anyone will be able to tell a difference. If it had an oil temp gauge, maybe there would be a slight difference in oil temp when towing, but I bet it would be minimal. (Between 20 wt and 40 wt)
 
Originally Posted By: Shannow
Originally Posted By: tig1
Oh NO!! Another "Thick VS Thin" thread!
28.gif
18.gif
Trolling.gif



Here it is another tig1 post that he didn't get in first extolling the fact that he ran 5W20 before Ali Hass, in an engine that called for 10W40, and showing the flogging horse emoticon.


+117
 
Originally Posted By: aquariuscsm
Some manuals these days only list one oil,like my Accord which only lists 0W20.


Back in 1999 Ford and Honda submitted to the EPA 5w-20 oil for approval in MPG testing. In 2000 the EPA granted Ford and Honda approval. HOWEVER, in the approval letter (I have a copy) the EPA stated THAT ONLY 5w20 could be used as factory fill AND THE ONLY OIL APPROVED for use in the factory manual. My 2005 Ford Ranger OM only list's 5w20 for the 3.0l. 5w30 is approved for the 4.0l because Ford had issues with the oil pump (not bearing clearances). My OM also states that 5w20 in the 3.0l provides "adequate" protection. I researched the 3.0l from it's beginning and found a few block alterations for strengthening and noise vibration and changing piston design to a lighter piston and making the 1st compression ring smaller and moving it closer to the crown of the piston. Nothing was done to bearing clearances, oil pump design or machining practices. The original 3.0l was designed for 5w30 so that's what I use.
 
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